Typically large uninterrupted power supply (UPS) installations involve locating the backup system in a central area and distributing the power, through standard breaker panels and branch circuits, to many power supplies in separate areas of the facility. This type of system is generally not of concern until one of the branch circuits experiences an overload or short circuit condition which affects some or all of the other loads which are connected to the output of the same UPS. Standard panels, at the time of a short circuit, drop to a zero (0) voltage level resulting in all loads connected to the panel experiencing a loss of power causing re-boots, opened contacts, etc. During the duration of the short circuit the output voltage of the UPS drops to zero until that particular branch circuit breaker trips, removing the faulty equipment from the system.
The length of time required to clear the breaker has a major effect on the rest of the system, due to the limited ride-through capabilities of a typical power supply. Most equipment will be affected should the power be interrupted for a period greater than 1 cycle at rates frequency. It then becomes important that the short circuit fault duration does not exceed this specification.